The long-term goal of his work is to integrate cellular and molecular methods to provide an understanding of the control of animal morphogenesis. This proposal focuses on three key morphogenetic processes common to all animal embryos: 1) directional migration of embryonic cells, 2) cell rearrangements within epithelial sheets, and 3) size regulation. These problems will be addressed in the optically clear, manipulable sea urchin embryo. 4-D fluorescence microscopy is to be used to analyze cell movements in vivo. cDNA library screening will be used to identify potential regulatory molecules involved in these movements. Experiments are proposed that build on recent biochemical studies in Dr. Ettensohn's laboratory demonstrating a role for a specific extracellular matrix determinant in epithelial cell rearrangements during gastrulation. The problem of size regulation will be analyzed with respect to skeletal morphogenesis, using embryo manipulation, cell-type specific molecular markers, and an in vitro skeletogenesis system.